NO339445B1 - Borehole treatment agents having a low toxicity oil phase and their use - Google Patents

Description

The present invention relates to borehole treatment agents which contain an aqueous phase and an oil phase, whereby the oil phase exhibits particularly low toxicity values towards marine small, living organisms and the use of such borehole treatment agents.

Borehole treatment agents are all types of auxiliary fluids that are used when drilling oil or natural gas deposits. As characteristic examples of such treatment agents, the invention will be described below with the help of drilling fluids and drilling muds which are built up on the basis of such fluids, and which find use both in land-based and in sea-based drilling. However, the scope of application of the invention when modifying excipients of the kind in question here is not limited to this. Further, numerous liquids are taken into consideration in the subject area described here. Examples include spotting fluid, spacers, packing fluids, auxiliary fluids for workover and stimulation and for fracturing. The scope of the invention thereby includes both auxiliary liquids of the aforementioned type which are oil-based, i.e. working with a closed or continuous oil phase, but also auxiliary substances in which the oil phase is emulsified in a particularly aqueous, continuous phase. Drilling fluids or drilling mud that is built up on these are characteristic examples of the various possibilities.

On the one hand, water-based drilling fluids with a content of around 1 to 50% emulsified oil phase are known, alongside other, common auxiliary substances in such a drilling fluid, which are also referred to as oil-in-water emulsion mud fluids. On the other hand, oil-based sludge systems are also generally used where the oil is the pourable phase or at least forms a significant proportion of this phase as a continuous oil phase. Of particular importance here are the so-called invert drilling muds which, on the basis of water-in-oil emulsions, contain a dispersed, aqueous phase in the continuous oil phase. The content of dispersed aqueous phase is usually in the range of at least about 5 to 10% by weight up to about 50 to 60% by weight. Alongside these water-in-oil invert drilling muds, however, so-called "true-oil muds" are also known, where the liquid phase consists, so to speak, exclusively of a continuous oil phase which possibly contains small amounts, usually no more than around 5 to 10% by weight, of aqueous phase in dispersed form.

The non-aqueous phase in such sludge systems is formed by the so-called carrier fluid. This usually involves diesel oil, to which special additives have been added that make up the actual drilling fluid. In the late 1980s, however, came the need for environmentally friendly sludge systems and thereby also carrier fluids. In particular, these were to be better biodegradable than the diesel oil then used. Alongside various liquid esters, such as those described for example in EP 0 374 672 A1, olefinic hydrocarbons were also examined with regard to their usability. Here, for example, reference should be made to EP 0 765 368 A1 and US 586 9434 A, which have as their subject the use of so-called α-olefins as a carrier fluid.

However, there is still a need for new carrier fluids, as the known compounds are not always usable under all application conditions and do not meet the ever-increasing requirements for biodegradability and low toxicity. The latter criterion in particular is becoming increasingly important, as more and more boreholes are to be drilled into ecologically sensitive areas. This particularly applies to the so-called offshore drilling, i.e. drilling that is carried down from the seabed.

The determination of the toxicity of a drilling mud therefore usually takes place by biological testing where small living marine organisms are exposed to components in the drilling fluid in different concentrations. The purpose is to find systems that meet both the physical and technical requirements and that also exhibit the lowest possible toxicity in relation to the outside world. At this point, reference must also be made to the physical load on such drilling mud. These are heated at great depths to temperatures of up to 250°C and more, high pressure prevails and, above all, the compound in the material must at the same time both remain chemically stable and maintain its viscosity behavior without significant changes and in addition under the mentioned conditions also form stable emulsions.

The task of the present invention is to provide borehole treatment agents or well treatment agents, in particular drilling mud or drilling fluids, which are improved both with regard to the technical application properties and in terms of ecological acceptability.

The object of the present invention is therefore borehole treatment agents containing an aqueous phase and a non-aqueous oil phase, emulsifiers and possibly further additives such as weighting agents, fluid loss additives, viscosity-regulating additives, cross-linking agents, salts, biocides, corrosion inhibitors and/or an alkali reserve, whereby it does not -aqueous phase in whole or in part is selected from the group:

a) paraffins with 5 to 22 carbon atoms, and/or

b) internal olefins with 12 to 30 C atoms in the molecule,

in each case in admixture with

c) carboxylic acid esters of the general formula R-COOR-R, where R is a straight or branched, saturated or unsaturated alkyl radical with 15 to 25 C atoms and R' is a

saturated, straight or branched alkyl residue with 3 to 22 C atoms,

and which is characterized by the quotient between the toxicity for internal olefins with chain length C16/C18 (standard IQ) and the toxicity for the constituents in the non-aqueous phase, all measured according to the Leptocheirus plumulosus acute, static 96-hour/10-day sediment toxicity test (in according to ASTM E 1367 -92 & EPA/600/R-94/025, Part 11) is less than 1.

A further object of the present invention is the use of the above-mentioned borehole treatment agents.

The toxicity testing using the above-mentioned Leptocheirus test according to ASTM E 1367 is prescribed by the Environmental Protection Agency (EPA) for such drilling mud systems to be used in drilling in the Gulf of Mexico. To facilitate comparability between the results, the toxicity of a standard compound, namely a mixture of internal olefins with chain length C16/C18, is compared with the results of the carrier fluids to be tested. The quotient F or the relative toxicity is then obtained as follows: F = toxicity (standard) / toxicity (carrier fluid). The sludges according to the present invention contain oil phases whose value for F is less than 1, preferably less than 0.5 and in special cases less than 0.4.

As the toxicological studies show, hydrocarbons in connection with Leptocheirus plumulosus results are to be considered distinctly critical. The following tables support this statement:

All the more surprising were the results where esters, based on total C chain C16 - C26, were able to set the total toxicity of mixtures of hydrocarbons with esters to the criteria required by EP A. Examples of mixtures with the respective F-values:

OMC586 means a 2-ethylhexanol ester based on saturated C8-C14 fatty acids. OMC233 corresponds to an isobutanol ester based on C14-18 + C16-18 unsaturated fatty acids. OMC1049 means an octanoic acid 2-ethylhexyl ester. All products are supplied by the company Cognis.

The results show that of the products already used in practice such as branched paraffins, LAO 14/16, low-toxic mineral oil and IO-C16/18, the two products Cl4/16 LAO and the low-toxic mineral oil (without representative ester addition) could be adjusted to the EPA reference substance data (IO C16/18 from the company Chevron). This is, especially when it comes to LAO, surprising, as branched paraffins usually exhibit higher toxicity. However, these data show that it is possible to achieve drilling mud systems based on IO as well as paraffin oils (straight or branched) using the invention's addition of esters or ester mixtures, which achieve a Leptocheirus-Tox-Factor < 1.

The oil phase for the systems of the invention contains components a) and/or b) alone or together in admixture with esters c) and possibly in admixture with other, suitable oil phases.

Component a)

According to the invention, straight or branched paraffins with 5 to 22 C atoms are used as component a). Paraffins, more correctly indicated as alkanes, are, as is known, saturated hydrocarbons as the straight or branched representatives according to the general formula CnH2n+i. The cyclic alkanes according to the general formula CnH2n. Straight and branched paraffins are particularly preferred, while cyclic paraffins are less preferred. Particularly preferred is the use of branched paraffins. Furthermore, such paraffins are preferred which are liquid at room temperature, i.e. those with 5 to 16 C atoms per molecule. However, it may also be preferred to use paraffins with 17 to 22 C atoms which exhibit a wax-like consistency. However, it is preferred to use mixtures of the different paraffins, whereby it is particularly preferred when these mixtures are still liquid at 21°C. Such mixtures can be formed, for example, from paraffins with 10 to 21 C atoms. When it comes to toxicity and particularly in the Leptocheirus plumulosus test, paraffins do not usually give sufficiently good results. Typical F-values for paraffins are between 2.7 to 4.53.

Component b)

Internal olefins (usually indicated as IO) can be used as components b), according to the invention. Thereby, IOs are likewise per se known compounds, which can be produced by the person skilled in the art in a per se known manner. EP 0 787 706 Al describes, for example, a method for the synthesis of IOs by isomerization of α-olefins on sulfonic or persulfonic acids. It is characteristic that the IOs obtained in this way are straight and contain at least one olefinic double bond which is not located in the a-position of the alkyl chain.

Such IOs or IO mixtures are preferably used which contain IO with 12 to 30 C atoms in the molecule, preferably 14 to 24 C atoms and especially with up to 20 C atoms in the molecule. Preferably, the olefins used in the invention have only one olefinic double bond. In the case of the Leptocheirus test, F values between 1.1 and 2.0 are generally obtained.

Component c)

Furthermore, esters of the general formula R-COO-R', where R is a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' is a saturated, straight or branched alkyl residue with 6 to 22 C- atoms, a component of the oil phases of the invention. Such esters are also known chemical compounds. Their principle use in drilling mud is, for example, the subject of EP 0 374 672 Al and EP 0 374 671 Al respectively. The Leptocheirus value for the esters is characteristically in the range 1.5 to 0.2, so that such compounds can therefore be suitable for the formation of low-toxic oil phases. However, special chain lengths must then be selected. Particularly preferred is the use of such esters whose residue R stands for a saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' for a saturated alkyl residue with 3 to 10 C atoms. The saturated compounds are therefore particularly preferred. Within the scope of the invention, it is preferred that the oil phase, next to the esters according to the description above, contains a maximum of 15% by weight (calculated on the oil phase) of other esters with residues R, which stand for alkyl residues with more than 23 C atoms.

Drilling mud is described which, in addition to the aqueous phase, such as the oil phase, contains only esters of the above-mentioned formula, the toxicity of which, measured according to the Leptocheirus test, is less than 1 compared to standard IO. The present invention therefore also requires drilling mud containing an aqueous and a non-aqueous oil phase, emulsifiers and possibly other additional additives, such as for example weighting agents, fluid loss additives, viscosity-regulating additives, crosslinkers, salts, biocides, corrosion inhibitors and/or an alkali reserve, whereby the the non-aqueous phase is more than 50% by weight selected from the group of esters of the general formula R-COO-R' where R stands for a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' is a saturated, straight or branched alkyl residue with 3 to 10 C atoms, whereby the non-aqueous phase has a relative toxicity, i.e. the quotient between the toxicity of internal olefins with chain length C16/C18 (standard IO) and the toxicity of the components of the non-aqueous phase, in each case measured according to the Leptocheirus plumulosus acute, static 96-hour/10-day sediment toxicity test (according to ASTM E 1367 - 92 & EPA/600/R-94/025, Part 11) , of less than 1.

In addition to components a) and/or b) and c), there may also be other, water-insoluble components in the oil phases to the extent that these are ecologically acceptable. Further, particularly suitable mixture components in the oil phase of the invention are therefore in greater detail: (i) esters of Cl-5 monocarboxylic acids and 1- and/or polyfunctional alcohols, whereby residues of 1-hydric alcohols exhibit at least, and preferably at least 8 C atoms , and the polyhydric alcohols preferably have 2 to 6 C atoms in the molecule, (ii) mixtures of secondary esters, selected from the group propyl carboxylate, butyl carboxylate, pentyl carboxylate, hexyl carboxylate, heptyl carboxylate, octyl carboxylate, nonyl carboxylate, decyl carboxylate, undecyl carboxylate, dodecyl carboxylate, tridecyl carboxylate, tetradecyl carboxylate , pentadecyl carboxylate, hexadecyl carboxylate, heptadecyl carboxylate, octadecyl carboxylate, nonadecyl carboxylate, eicosyl carboxylate, uneicocarboxylate, doeicosyl carboxylate and isomers thereof, whereby the secondary esters in each case exhibit a carboxylate residue with 1 to 5 C atoms, water-insoluble ethers of monohydric alcohols with 6 to 24 C -atoms,

(iii) water-insoluble alcohols with 8 to 36 C atoms,

(iv) poly-α-olefins (PAO) and α-olefins, and

(v) mixtures of components (i) to (iv).

However, linear α-olefins with chain lengths C14/C16 and so-called low-toxicity mineral oils are excluded from co-use, as these also do not give the desired toxicity values in the invention's mixture with esters from group c). Likewise, the co-use of diesel oil is excluded. In addition, co-use of methyl esters is excluded as these are not suitable due to their high toxicity, when it comes to obtaining low-toxic oil phases within the context of the invention. However, under special conditions, the co-use of such components may be necessary, but the amounts used in these cases do not exceed 5% by weight, preferably a maximum of 2% by weight, calculated on the oil phase.

As a further, mandatory component, the agents of the invention contain emulsifiers. When it comes to choosing such, the type of drilling mud is decisive. Practical usable emulsifiers for the formation of water-in-oil emulsions are particularly selected, oleophilic fatty acid salts, and especially those based on amidoamine compounds. Examples of these are described in the already mentioned US-PS 4,374,737 and the literature indicated there.

For the production of water-in-oil emulsions, however, other, preferably non-ionic emulsifiers are also used. From the large range of non-ionic emulsifiers, emulsifiers which according to the invention are particularly suitable can at least be assigned to one of the following classes: (oligo)-alkyloxylates, especially lower-alkyloxylates, whereby here corresponding ethoxylates and/or propoxylates are particularly important, of basic molecules containing lipophilic residues and capable of alkylation, of natural and/or synthetic origin. Thereby, low in this context means values from 2 to 15 and especially 2 to 10 parts alkoxide per molecule emulsifier. A further, important class of non-ionic emulsifiers for the purposes of the invention are partial esters and/or partial ethers of polyfunctional alcohols with in particular 2 to 6 C atoms and 2 to 6 OH groups and/or their oligomers with lipophilic residual acids and/ or alcohols. Compounds of this type which in addition contain (oligo)-alkoxy residues in the molecular structure and thereby particularly corresponding oligo-ethoxy acid residues in the bound state are therefore particularly suitable. A further example of corresponding emulsifier components are alkyl (poly) glycosides of long-chain alcohols as well as the already mentioned fatty alcohols of natural and/or synthetic origin, respectively alkylolamides, amine oxides and lecithins. Without claiming to be complete, the following suitable emulsifier components must also be mentioned from the classes of substances summarized here: (oligo)-alkoxylates of base molecules containing lipophilic residues can in particular be derived from selected representatives from the following classes of basic molecules containing lipophilic residues: fatty alcohols, fatty acids, fatty amines, fatty amides, fatty acid and/or fatty alcohol esters and/or ethers, alkanolamides, alkylphenols and/or their reaction products with formaldehyde as well as further reaction products of carrier molecules containing lipophilic residues with lower alkoxides. Examples of partial esters and/or partial ethers of multifunctional alcohols are in particular the corresponding partial esters with fatty acids, for example from the technique comprising glycerin mono- and/or diesters, glycol monoesters, corresponding partial esters of oligomerized, multifunctional alcohols, sorbitan partial esters and the like, as well as similar compounds with ether groups.

The oil phase is preferably formed by mixing the components a) and/or b) with the ester oils c) in a weight ratio of 10:1 to 1:1, preferably 5:1 to 1:1 and especially 3:1 to 1:1, in order to reach the desired relative toxicity.

Borehole treatment agents according to the invention are preferably available as water-in-oil emulsions, i.e. that a homogeneous oil phase surrounds a finely dispersed, aqueous phase. Particularly preferred is the execution of the present agents according to the invention as drilling mud. The agents of the invention are preferably present in a weight ratio between aqueous and oil phase of 50:50 to 1:99, preferably 30:70 to 20:80 and especially 10:90. Thereby, it is preferred that the oil phase consists of at least 50% by weight, preferably at least 80% by weight and in particular at least 90% by weight of compounds a) and/or b) and c). Furthermore, such borehole treatment agents are preferred if the oil phase is formed in at least 50% and preferably at least 80%, especially 100% of the components a) to c). The weight-% value refers here to the weight of the oil phase.

It may be advantageous for the non-aqueous oil phase to consist of the agents of the invention with 100% by weight of mixtures of components a) and/or b) and c). Furthermore, it can be advantageous when only mixtures of a) and c) or preferably only b) and c) are contained in the oil phase of the agents of the invention.

Since the oil phase in the agents of the invention preferably has pour points below 0°C, preferably below -5°C (measured according to DIN ISO 3016: 1982-10). The Brookfield viscosity of the oil phases is at most 50 mPas at 0°C. The well or borehole treatment agents of the invention exhibit, to the extent formed as oil-based drilling mud of the water-in-oil type, a plastic viscosity (PV) in the range of 10 to 70 mPas and a yield point (Yield-Point YP) of 5 to 160 lb/100 ft<2>, in each case determined at 50°C. The kinematic viscosity of the oil phase, measured according to Ubbelohde at 20°C, should preferably amount to no more than 12 mm<2>/second. The aqueous phase in the agents of the invention preferably exhibits a pH value in the range 7.5 to 12, and in particular 7.5 to 11, and especially 8 to 10.

In addition to the ingredients listed above, the agents of the invention also contain additives such as weighting agents, liquid loss additives, viscosity-regulating additives, crosslinkers, salts, biocides, corrosion inhibitors, and/or an alkali reserve. Here, the general legal requirements for the composition of the treatment fluids apply, as they will be summarized below using the corresponding drilling mud. The additives can be water-soluble, oil-soluble and/or water- or oil-dispersible.

Classic additives can be: fluid loss additives, structure viscosity-building, soluble and/or insoluble substances, alkali reserves, agents to inhibit unwanted water exchange between the drilled formation, for example water-swellable clays and/or salt layers, and the for example water-based drilling mud fluid, crosslinkers for better attraction of the emulsified oil phase on solid surfaces, for example to improve the lubrication effect, but also to improve the oleophilic closure of exposed formations such as rock surfaces, biocides, for example to inhibit bacterial attack on oil-in-water emulsions and the like. Only as an example should be mentioned: finely dispersed additives to increase the mud density: Barium sulphate and (baryte) are widely distributed, but also calcium carbonate (calcite) or the mixed carbonate of calcium and magnesium (dolomite).

Agents for building up the structural viscosity and which at the same time act as fluid loss additives: In the first line, bentonite or hydrophobic bentonite should be mentioned here. For saltwater mud, other, comparable clays, and especially attapulgite and sepiolite, have a significant practical significance.

Co-use of organic polymer compounds of natural and/or synthetic origin can also have a significant impact in these contexts. Particular mention must be made of starch or chemically modified starches, cellulose derivatives such as carboxymethyl cellulose, guar gum, syntan gum or also pure, water-soluble and/or water-dispersed polymer compounds and in particular of the type of high molecular weight polyacrylamide compounds with or without anionic or cationic modification. Thinners for viscosity regulation: The so-called thinners can be organic or inorganic, examples of organic thinners are tannins and/or Qebracho extract. Further examples are lignite and lignite derivatives, and particularly lignosulfonates.

As already mentioned, in a preferred embodiment of the invention, the co-use of toxic components is waived, precisely here in the first place the corresponding salts with toxic heavy metals such as chromium and/or copper. Additives that prevent the unwanted water exchange with, for example, clays: The additives known from the prior art in connection with oil- and water-based drilling mud are taken into account here. In particular, it concerns halides and/or carbonates of alkali and/or alkaline earth metals, whereby corresponding potassium salts can have a particular significance in combination with lime.

Alkali reserves: In consideration here, they come to the overall behavior of the sludge-tuned, inorganic and/or organic bases, in particular corresponding basic salts respectively hydroxides of alkali and/or alkaline earth metal salts as well as organic bases. Particularly preferred here is the use of lime (Ca(OH)2) as an alkali reserve. Typical lime content in drilling mud is between 1 and 6 lb/bbl, whereby the decisive factor depends on the type and composition of the oil phase, when it comes to which quantities can be used. The type and amount of these basic components are preferably selected and coordinated in such a way that, in the case of hydrolysis-prone esters, especially unsaturated esters with carbon numbers C16 to C24, excessive hydrolysis does not occur, as the corresponding reaction products, in particular the fatty acids, can affect the stability for the emulsion drilling mud. In these cases, it is preferred to make available an alkali reserve in the sludge which corresponds to a maximum concentration of 2 lb/bbl of the basic components, preferably lime in the sludge, under working conditions.

When it comes to organic bases, a conceptual distinction must be made between water-soluble organic bases, for example compounds of the diethanolamine type, and in practice water-insoluble bases of a distinctly oleophilic nature. Precisely the co-use of such oil-soluble bases within the scope of the invention lies within its teachings. Oleophilic bases of this type, which are particularly distinguished by at least one longer hydrocarbon residue with, for example, 8 to 36 C atoms, are thus not dissolved in the aqueous phase, but in the oil phase. Here, this basic component has several meanings. On the one hand, it can immediately act as an alkali reserve, on the other, the dispersed oil droplets provide a certain positive charge state and thereby lead to increased interaction with negative surface charges such as these can be found in particular with hydrophilic clays that are capable of ion exchange. According to the invention, the influence on the hydrolytic cleavage and the oleophilic closure of water-reactive stone layers can thereby be taken into account. The amount of auxiliaries and additives used in each case is in principle within the usual limits and can be obtained from, among other things, the cited literature.

The use of esters in group c) in admixture with component a) and/or b) means that oil phases with relatively low toxicity to the marine, living micro-organisms Leptocheirus plumolosus can be obtained.

Furthermore, by adding esters of the general formula R-COO-R', where R means a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms, and R' means a saturated, straight or branched alkyl residue with 3 to 10 C atoms, the lubricating properties of the drilling muds, containing an aqueous phase and a non-aqueous oil phase, emulsifiers and possibly further additives such as weighting agents, fluid loss additives, viscosity-regulating additives, crosslinkers, salts, biocides, corrosion inhibitors and/or a alkali reserve, clearly improved. Preferably, between 5 and 15% by weight, and in particular 8 to 12% by weight, of these esters are used in the oil phase to achieve the desired lubrication effect.

Furthermore, by adding esters with the general formula R-COO-R' where R means a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' means a saturated, straight or branched alkyl residue with 3 to 10 carbon atoms, in oil phases of normal drilling mud, reduce the use of structure formers, preferably products based on possibly chemically or physically modified clays such as bentonite. As regards details, reference should be made to the available literature, for example reference may be made to the "Manual of Drilling Fluid Technology", NL Baroid 1979, Chapter "Fundamental Characteri sties of Drilling Fluids" and in particular what is described on pages 5 to 8. Thereby significant cost savings are achieved according to sludge according to the known technique. The use of the esters used in the invention is therefore between 15 and 100% by weight, and preferably 25 to 100% by weight, and especially 50 to 100% by weight, calculated on the amount of the oil phase. With the help of the oil phases of the invention, the proportion of clay-based structure formers can be significantly reduced. It is even possible to formulate clay-free sludges. Preferably, the esters are used within the scope of the invention for emulsion drilling mud of the invert type, i.e. the water-in-oil type.

EXAMPLES

In the following, examples of the invention's lower-toxic drilling mud will be given: Four different muds were produced which were based on the following framework recipe:

01je:water ratio: 80:20

Example 1

For Example 1, a 50:50 weight mixture of 0.284 bbl of an IO mixture of IOs with C16/C18 and a saturated monocarboxylic acid ester based on monocarboxylic acids with 20 to 22 C atoms and 2-ethylhexanol (OMC 586, company Cognis). The F value was 0.87.

In the following tables are the rheological values before and after 16 hours of aging of the sludges at 250°F. The measurements of the rheological data always took place in accordance with API bulletin RP 13 B-2.

Comparative example 1

The sludge in the comparative example was contained in the oil phase only in the IO mixture based on IO with C16/C18. However, the F-value was 2.7.

It could be demonstrated that the use of the ester-paraffin mixture allowed for the production of lower-toxic drilling muds without any limitation of the use properties.

Example 2

For Example 2, a slurry analogous to Example 1 was used, but the content of fluid loss additives was reduced to 4 lb. The F value was 0.87.

Comparative example 2

Once again, a sludge with only IO in the oil phase was used as a comparison example.

Example 3

The following table shows the comparison of oil phases based on paraffin with an oil phase based on paraffin:ester 1:1 (ester:OMC586). The kerosene in question was from the company Petro Canda, of the Puredrill IA-35 type. The remaining components of the sludge corresponded to the framework recipe above.

Examples after aging (161, 250°F), oil/water: 80:20

Example before aging:

As can be read from the results above, it is possible to formulate systems based on paraffin-ester mixtures with clearly reduced geltone contents. Attempts to achieve such effects using mixtures of various aromatic-free/poor hydrocarbons were not successful.

A further important criterion is the base viscosity of the oil phase. It was measured here according to Ubbelohde, at 20°C with capillary factors c = 0.009987, c = 0.009933, c = 0.029. The kinematic viscosity can be found from the formula v = A t x c. All esters were based on 2-ethylhexanol.

Examples:

Claims (25)

1. Borehole treatment agent containing an aqueous phase and a non-aqueous oil phase, emulsifiers and possibly further, common additives such as weighting agents, fluid loss additives, viscosity-regulating additives, cross-linkers, salts, biocides, corrosion inhibitors and/or an alkali reserve, whereby the non-aqueous phase completely or partially is selected from the group a) paraffins with 5 to 22 C atoms and/or b) internal olefins with 12 to 30 C atoms in the molecule, in each case in admixture with c) carboxylic acid esters of the general formula R-COO- R', where R means a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' means a saturated, straight or branched alkyl residue with 3 to 22 C atoms, characterized in that the quotient between toxicity of internal olefins with chain length C16/C18 (standard IO) and the toxicity of the constituents in the non-aqueous phase, all measured according to the Leptocheirus plumulosus acute static 96-hour/10-day sediment toxicity test ten (according to ASTM E 1367 - 92 & EPA/600/R-94/025, Part 11), is less than 1. 2. Agent according to claim 1, characterized in that it is available as a water-in-oil emulsion. 3. Agent according to claim 1 or 2, characterized in that it is formed as a drilling mud. 4. Agent according to any one of claims 1 to 3, characterized in that the weight ratio between aqueous and oil phase is 50:50 to 1:99, preferably 30:70 to 20:80, and especially 10:90. 5. Agent according to any one of claims 1 to 4, characterized in that the oil phase consists of at least 50% by weight, preferably at least 80% by weight, and in particular at least 90% by weight of compounds a) and/or b) and c). 6. Agent according to any one of claims 1 to 5, characterized in that component a) is selected from the group of straight or branched paraffins with 10 to 21 C atoms, whereby branched paraffins are particularly preferred. 7. Agent according to any one of claims 1 to 6, characterized in that component b) is selected from the group of internal olefins with 12 to 30 C atoms, preferably 14 to 24, and in particular up to 20 C atoms. 8. Agent according to any one of claims 1 to 7, characterized in that component c) is selected from esters of the formula R-COOR', where R means saturated or unsaturated, straight alkyl residues with 15 to 23 C atoms, and R' is a straight or branched, saturated alkyl radical with 6 to 22 C atoms. 9. Agent according to any one of claims 1 to 8, characterized in that, next to esters according to claim 7, a maximum of 15% by weight, calculated on the oil phase, of esters with residues R which stand for alkyl residues with more than 23 C atoms is contained. 10. Agent according to any one of claims 1 to 9, characterized in that the non-aqueous oil phase consists of 100% of compounds a) and/or b) and c). 11. Agent according to any one of claims 1 to 10, characterized in that the non-aqueous oil phase contains at least 50% by weight, preferably at least 80% by weight and in particular up to 100% by weight of mixtures of the compounds b) and c). 12. Agent according to any one of claims 1 to 11, characterized in that, in addition to the compounds a) to c), further, ecologically acceptable, water-insoluble components are also contained. 13. Agent according to any one of claims 1 to 12, characterized in that esters of Cl-C5 monocarboxylic acids with 1- and/or polyfunctional alcohols are used as additional components, whereby the alcohols have at least 6, preferably at least 8 and the polyhydric alcohols have 2 to 6 C atoms in the molecule. 14. Agent according to any one of claims 1 to 13, characterized in that mixtures of secondary esters are contained as further components, selected from the group propyl carboxylate, butyl carboxylate, pentyl carboxylate, hexyl carboxylate, heptyl carboxylate, octyl carboxylate, nonyl carboxylate, decyl carboxylate, undecyl carboxylate, dodecyl carboxylate, tridecyl carboxylate, tetradecyl carboxylate . 15. Agent according to any one of claims 1 to 14, characterized in that the non-aqueous oil phase exhibits a pour point below 0°C, preferably below -5°C. 16. An agent according to any one of claims 1 to 15, as an oil-based drilling mud of the water-in-oil type having a plastic viscosity (PV) in the range of 10 to 70 mPas and a yield-point YP of 5 to 60 lb /100 ft<2>, all determined at 50°C, characterized in that the non-aqueous oil phase exhibits a Brookfield viscosity at 0°C of no more than 50 mPas. 17. Agent according to any one of claims 1 to 16, characterized in that as oil-based drilling mud of the water-in-oil type it exhibits a plastic viscosity (PV) in the range of 10 to 60 mPas and a yield point (Yield-Point YP) of 5 to 40 lb/100 ft<2>, all determined at 50°C. 18. Agent according to any one of claims 1 to 17, characterized in that the oil phase exhibits a viscosity according to Ubbelohde at 20°C of a maximum of 12 mm<2>/sec. 19. Agent according to any one of claims 1 to 18, characterized in that the aqueous phase exhibits a pH value in the range 7.5 to 12, preferably 7.5 to 11, and most preferably 8 to 10. 20. Agent according to any one of claims 1 to 19, characterized in that the non-aqueous oil phase contains mixtures of components a) or b) and c) in a weight ratio of 10:1 to 1:1, preferably 5:1 to 1:1 , and especially 3:1 to 1:1. 21. Agent according to any one of claims 1 to 20, characterized in that it contains non-aqueous components b) whose relative toxicity in relation to IO with chain length C16/C18 is greater than 1, whereby compounds c) must be contained in the non-aqueous the oil phase. 22. Use of a borehole treatment agent according to any one of claims 1 to 21, comprising mixtures of a) straight or branched paraffins with 10 to 22 C atoms and/or b) internal olefins with 12 to 30 C atoms in the molecule with c) carboxylic acid esters with the general formula R-COO-R', where R means a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' means a saturated, straight or branched alkyl residue with 3 to 22 C atoms , for the production of invert drilling mud with low toxicity. 23. Use of a wellbore treatment agent according to any one of claims 1 to 21, comprising esters of the formula R-COO-R', where R means a straight or branched, saturated or unsaturated alkyl radical with 15 to 25 C atoms and R' means a saturated , straight or branched alkyl residue with 3 to 22 C atoms, as a mixture component in invert drilling muds containing paraffins and/or internal olefins as constituents, to reduce the toxicity of the oil phase of the invert drilling muds, measured according to Leptocheirus plumulosus acute , the static 96-hour/10-day sediment toxicity test (per ASTM E 1367 - 92 & EPA/600/R-94/025, Part 11). 24. Use of a borehole treatment agent according to any one of claims 1 to 21, comprising esters of the general formula R-COO-R', where R is a straight or branched, saturated or unsaturated alkyl residue having 15 to 25 C atoms and R' is a saturated, straight or branched alkyl residue with 3 to 10 C atoms, as an addition to drilling mud, containing an aqueous phase and a non-aqueous oil phase, emulsifiers and possibly further additives such as, for example, weighting agents, fluid loss additives, viscosity-regulating additives, crosslinkers, salts , biocides, corrosion inhibitors and/or an alkali reserve, to improve the lubrication properties of drilling mud. 25. Use borehole treatment agent according to any one of claims 1 to 21, comprising esters of the general formula R-COO-R', where R is a straight or branched, saturated or unsaturated alkyl residue with 15 to 25 C atoms and R' is a saturated, straight or branched alkyl residue with 3 to 10 C atoms, as an addition to drilling mud, containing an aqueous phase and a non-aqueous oil phase, emulsifiers and possibly further additives such as weighting agents, fluid loss additives, viscosity-regulating additives, cross-linking agents, salts , biocides, corrosion inhibitors and/or an alkali reserve, to reduce the proportion of structure formers on the basis of possibly chemically or physically modified clays.